Shunt-regulator for variable-speed motors.



J. G. STIRK.

SHUNT REGULATOR FOB. VARIABLE SPEED MOTORS.

APPLICATION FILED JAN.26, 1911.

Patented Oct. 13, 1914.

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J. G. STIRK. SHUNT REGULATOR FOR VARIABLE SPEED MOTORS.

APPLICATION FILED JAN. 26, 1911.

Patented Oct. 13, 1914.

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JOHN GEORGE STIRK, OB HALIFAX, ENGLAND.

SHUNT-REGULATOR FOB VARIABLE-SPEED MOTORS.

Specification of Letters Patent.

. Application filed January 26, 1911. Serial No. 604,893.

To all whom it may concern:

Be it known that I, J 0111's GEORGE S'rmK,

a subject of the King of Great Britain, re-

siding at Halifax, in thecounty of York, England, have invented a newand useful Improvement in Shunt-Regulators for Teri able-Speed Motors,of which. the following is a specification.

This invention relates to apparatus for protecting motors with shuntcontrol agalnst being started on weak field, while provid ing for theautomatic return to a predeter mined speed after all resistance has beencut out of the armature circuit; and the essential feature is the use oftwo contact. arms to the shunt resistance, one of which may be left atany desired point while the other must either be full on or full off.

The apparatus consists of a resistance divided into a suitable number ofsections to be inserted in the shunt field of the motor. The varioussteps of the resistance are connected to separate studs of two multipleway switches. One of these switches serves for the customary adjustmentof the speed of the motor by hand or otherwise; or in the case of boringand turning mills, lathes, or the like, may be operated by the tool postand so insert resistance as the tool travels toward the center, thusspeeding up the motor as the diameter decreases and vice-versa.

The purpose of the second multiple switch is to obviate starting themotor on a weak en d field. The contact finger of this switch may becontrolled by a solenoid and dashpot. By the efiect of gravity .or aspring, the position of the switch when current is off is in theresistance all out.

After the motor has been started and accelerated to full normal speed,the solenoid is energized and the contact finger pulled to theresistance all in position, the motor being speeded up to the pointcorresponding with the'position of the contact finger of the firstmultiple switch.

Although in the foregoing the use of an automatic solenoid controlledstarter is assumed, the devicemay equally well be applied to ordinaryswitch gear. Further, in certain cases the two multiple switchesreferred to may be combined in one, provided that one is fitted with twoswitch arms or Description of drawings.-Figure 1 illustrates a combinedstarter and regulator for ordmary hand operation constructed accordingto my invention. Fig. 2 shows a modifi cation of combined starter andregulator shown atFig. 1. Fig. 3 shows diagrammatically my invention andthe wirings connected with theshunt contacts only. Fig. 4 shows completeset of foolproof switch gear with my invention applied.

Similar letters refer to similar parts throughout the several views.

With reference to Fig. 1, A are the armatnre resistance contacts, B theshunt resistance contacts, and C the common contact arm. D -is anindependently excited hold on coil, and E theoverload release coil, allelectrically connected by the customary wirings in the ordinary way. Fis a separately operated multiple switch whose studs are interconnectedwith the studs ofthe shunt resistances.

When desiring to start the motor the common contact arm 0 is moved byhand,

and in the first portion of its movement cuts out resistance in thearmature circuit A. in the latter part of its movement it operates onthe shunt field of the motor. 1 to 10 on switch B are connected to likestuds on the separately operated multiple switch F, see Fig. 3, which isconnected in turn to the shunt resistance. l

Assuming separate multiple switch F to be at the resistance all inposition (that is, in contact with No. 10 stud), operating the switcharm C causes the motor to start and. attain normal speed by armatureresistance A being cut out step by step in the customary way; aftercontact arm 0 leaves elongated stud 1 on shunt resistance B, the motoris thenpaccelerated by resistance being inserted mop by step in theshunt field circuit; contact arm G being finally held at full onposition by magnet or coil D. If the multiple switch F is now operatedresistance may be cut out of the motor field and the speed of the motorvaried accords y- The contact arm F of switch 7 may be left at anydesired position indefinitely or until a further speed is decided upon,but inno case is the position of the arm F effected by any movement ofthe contact arm of the armature circuit.

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Patented Oct. 13, 1am.

Supposing the switch F is left at No. 4 stud as at Fi 1, and the motorsto ped, contact arm at once falls to the full off position, and onrestarting, the motor is provided with a full field which is retaineduntil all resistance is cut out of the armature circuit and the contactarm C leaves the elongated stud 1 on B. After this point the motor isgradually accelerated as aforesaid until No. 4 stud on B is reachedafter which no increase of speed occurs. Contact arm C is always eitherfull on by magnet D, or full ofi ,by gravity or spring, it cannot beleft at any intermediate position, but contact arm or switch F may beleft at any desired position. The placing of the resistance connected tomultiple switches F and B in series with the shunt field of a motorinsures the motor being started on full field, while by the adjustmentof the arm or switch F, the predetermined speed can be found each timewithout recourse to the objectionable and unreliable devices of countingthe studs or chalk-marking the slate.

At Fig. 2,'instead of two multiple switches for the shunt resistanceshaving their studs interconnected, a common multiple switch is usedhaving two contact arms working upon it. With contact arm F on stud No.5 as shown, and with contact arm C at full on position, the motor isrunning at a slightly accelerated speed. On stopping the motor, arm Ofalls to the ofi position, and on restarting, the motor starts on fullfield and accelerates to a speed corresponding to stud N0. 5 on multipleswitch B. While the motor is running its speed may be varied byadjusting contact arm F which is independent of contact arm O.

In the application of my invention to a complete set of foolproof switchgear, as shown at Fig. 4, the solenoid M is energized by pressing one ofthe start push buttons T, T. Main switch is thereby closed and solenoidN energized. The starter arm (not shown) is then steadily pulled upcutting out resistance in the armature circuit. On the starter armarriving at the top and all armature resistance being cut out, solenoidP is energized by carbon contacts R and wire S, and contact arm (notshown) on shunt regulator B is pulled to the full on position. The speedof the motor is in the manner before described governed by the positionof the contact finger A on multiple switch A. Assuming contact finger Ato have been left at No. 1 stud, resistance is steadily inserted in theshunt field of the motor until the maximum speed is attained. If contactfinger A was left at stud No. 12 contact finger of regulator B would bedrawn up without producing any effect whatever on the speedof the motor;while if contact finger A -was left at say No. 7

stud, contact finger of regulator B would be drawn up and the motoraccelerated in speed until No. 7 stud was reached, after which nofurther increase of speed would follow. l

Contact finger A may be operated either by hand, or by any suitablemeans connected to or operated by the slide of lathe, boring mill, orother appliance, or it may be controlled from a distance by twosolenoids alternately energized, or in any other convenient manner. Therate at which the solenoids pull up the switch arm may be governed bydaslipots. y

In the application of my invention to a complete set of foolproof switchgear, as shown at Fig. 4, the solenoid M is energized by conductor M onpressing one of the start push-buttons T, T. The main switch V is therebclosed and solenoid N is energized by con uctor M the circuit beingcompleted through conductor M and resistance M connected, to armaturecircuit. The starter arm N of multiple way switch N is then steadilypulled up, cutting out resistance M in the armature circuit. On thestarter arm arriving at the top and all armature resistance being cutout, solenoid P is energized by carbon contacts R, and conductor S, (thecircuit being completed through conductors R R resistance R strip R andconductor R connected to the shunt field), and contact arm 6 is pulledover the shunt resistance contacts B to the full on position. The speedof the motor is in the manner before described governed by the positionof the contact finger A on second multiple way switch A as fullyillustrated at Fig. 3 and partially illustrated here by the conductor13. and R connecting like studs of B with like studs of A. Assumingcontact finger A to have been left at No. 1 stud, resistance R issteadily inserted in the shunt field of the motor until the maximumspeed is attained. The circuit being traced through conductor R, contactarm O, strip R contact arm A resistance R strip R and conductor R to theshunt field and thence to the opposite main. If contact finger A wasleft at stud No. 12, contact finger O would be drawn up over theresistance contacts B without producing any effect whatever on the speedof the motor; the circuit being as before except that resistance R isout out by contact A making, direct contact between strips R and R Whileif contact finger A was left at say No. 7 stud, contact finger C wouldbe drawn up, and the motor accelerated in speed until No. 7 stud of B isreached after which no further increase of speed would follow. Thecircuit being through conductor R contact arm C, strip R contact arm Ato stud No. 7 of A, theme through the last 5 sections of resistance Rand to the shunt field through contact R and conductor R as beforedescribed.

What I do claim as my invention and desire to secure by Letters Patentis 1. A shunt regulator for controlling variable speed motors comprisinga resistance adapted to be inserted in the shunt field of the motor anddivided into a number of steps, two multiple way switches operatively'connected to the resistance,

each switch having studs and contact arms, circuits connecting the studsof one switch to the like studs of the other switch and cross connectingthe contact arms.

2. A shunt regulatorv forthe control of variable speed motors comprisinga resistance adapted to be inserted in the shunt field and divided intoa number of steps, a multiple way switch having segmental studs, meansfor cross connecting the contact arms and means for operativelyconnecting the contact arms to the resistance by the segmental studs.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

JOHN GEORGE STIRK. Witnesses:

WM. Rm, FRED HAMMOND.

